Muscular, brawny, sinewy, athletic, burly, husky are applied to persons in the sense of strong and powerful in build or physique.
Muscular implies well-developed, but not overdeveloped, muscles and, usually, a stalwart build.
Brawny implies the full development of the muscles; it carries no connotation of fatness but rather suggests the might that is associated with hard flesh and great size.
Sinewy attributes no less power to the muscles than brawny, but it suggests greater energy and quickness and seldom connotes hugeness. Rather it often implies a leanness, toughness, and litheness that are the result of training or of persistent exercise; thus, such people as blacksmiths, steelworkers, stevedores, and prizefighters are often described as brawny, but fencers, runners, and acrobats, more often as sinewy.
Athletic as used in anthropometry denotes a particular body build marked by heavy frame, large chest, and powerful well-developed muscles. In more general use athletic may suggest much the same type, but more often it stresses fitness for athletic activity and emphasizes muscularity, sinewiness, quick reflexes, and vigor of health and it is with this latter aspect that the term is usually extended to the mental life or its products.
Burly stresses massiveness of build to such an extent that it often carries connotations of corpulence, of coarseness, or of grossness and suggests the possession of brute force.
Husky implies a powerful athletic build and brawniness.